1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to managing multi-hop traffic.
2. Introduction
Various network topologies may be employed to establish wireless communication. For example, a wide area network, a local area network, or some other type of network may be deployed depending on the desired wireless communication capabilities.
A wireless wide area network may be implemented as a planned deployment within a licensed frequency band. Such a network may be designed to optimize spectral efficiency and quality of service to support a relatively large number of users. A cellular network is one example of a wireless wide area network.
A wireless local area network is often deployed without centralized planning. Such a network may be deployed, for example, in unlicensed spectrum utilizing an infrastructure-based architecture or ad hoc-based architecture. This type of network may typically support a relatively smaller number of users. A Wi-Fi network is one example of a wireless local area network.
In practice, the above networks may have various disadvantages due to tradeoffs that may be made to provide a given type of service. For example, due to the complexity of centralized planning, setting up a wireless wide area network may be relatively expensive. Moreover, this type of network may not effectively handle dynamic traffic flows. Hence, such a scheme may not be well suited for “hot spot” deployments. On the other hand, an unplanned wireless local area network may not achieve the same level of spatial efficiency (bits/unit area) as a planned network. Moreover, to compensate for potential interference between nodes in the network, an unplanned scheme may employ interference mitigation techniques such as carrier sense multiple access. In practice, however, interference mitigation techniques such as these may lead to poor utilization, limited fairness control, and susceptibility to hidden and exposed nodes.
U.S. Patent Application Publication No. 2007/0105574, the disclosure of which is hereby incorporated by reference, describes various techniques that may be advantageously employed in a wireless communication system. In some aspects such a system may employ timeslot-based communication where multiple wireless nodes in the system may simultaneously transmit and receive over a given channel during designated timeslots.
Here, fair-sharing of a wireless channel may be facilitated by joint scheduling of a transmission by a transmitter of one node and a receiver of another node. For example, a node that wishes to transmit may request a set of resources (e.g., one or more timeslots on one or more channels) based on knowledge of the availability of wireless resources in its neighborhood. In response to this request, a node that will receive the transmission may grant some or all of the requested channels based on the node's knowledge of the availability of wireless resources in its neighborhood. For example, a node that intends to transmit may learn of resource availability by listening to neighboring nodes that may receive when the node wishes to transmit. Conversely, a node that intends to receive may learn of potential interference by listening to neighboring nodes that may transmit when the node wishes to receive. In the event a node determines that its reception will or may be affected by neighboring transmissions, the node may transmit a resource utilization message (“RUM”) in an attempt to cause the neighboring nodes to limit their interfering transmissions. According to related aspects, RUMs may be weighted to indicate not only that a node is disadvantaged (e.g., due to the interference it sees while receiving) and desires a collision avoidance mode of transmission, but also the degree to which the node is disadvantaged.
A node that receives a RUM may utilize the fact that it has received a RUM, as well as the weight thereof, to determine an appropriate response. For example, a node may elect to abstain from transmitting or it may reduce its transmit power during one or more designated timeslots. Alternatively, the node may ignore the RUM if, for example, it has received a RUM that indicates that an associated node is more disadvantaged than any other nodes that transmitted RUMs. In this case, the node may elect to transmit to its associated node during the designated timeslot(s). The advertisement of weights may thus provide a collision avoidance scheme that is fair to all nodes in the system.